Increasing lope

[Widebody06]

From the help Mowton has given me, I'm wondering if beyond mixture issues, the reason my idle sounds mushy and blurry could be the PCM correcting things so much to maintain RPM precisely. My tune has adaptive error at 15 rpm and interger at 10. Wouldnt allowing a larger swing cause less computer adjustment? At some point I guess its easy enough to try it...in fact perhaps I need to try real time tuning so see if I can change those sort of things for the better without considering theory(which I dont have much of )
Anyway, what kind of error settings are you guys running with moderate to large cams? I'm referring to E40 LS2's

[Higgs Boson]

leave your idle table stock and mess with idle spark timing in the spark tab.

[mowton]

HB,

Why wouldn't you recommend "softening" the under/overspeed timing corrections at the low/mid RPM adjustment points to allow some of the natural cam lope to go unadjusted. Would reduce some of the "over correcting" and help settle the timing down on large cam setups.

Ed M

[Widebody06]

Higgs Boson, love the handle.
I'd love to know why you say that ....have you seen my tune? I do understand that the idle advance table does first order RPM control but seems to me that its only going to work properly IF the mixture is correct so that in effect the table does only minor corrections.
Up till my last VE table tweak, the spark table was pulling all of the advance out just to keep the RPM as it was setup. I have to log what the advance is now to see if I got it close enough to look to other factors but having the CEL go away tells me I'm pretty close.
My question in this thread basically is, IF I loosen the adaptive and integer error range, won't that cause less PCM input? Or put another way, wont it lope more? I can see for a mild cam with almost no overlap(which describes the stock cam) where my settings would be fine. But for a bigger stick, that wants to lope, such tight limits just seems like we are asking the PCM to counter the lope. So when the RPM tries to go up during lope, the PCM pulls advance out, RPM drops, it adds advance back and the cycle starts again. That is exactly what my log showed.

That may be the way to go, but unless loosing the error range can or will lead to oscillations I can't see any advantage to tying down lope.
And truthfully, I'd just as soon have a nice lope like we did back in the carb/no PCM days.

[Higgs Boson]

What are the cam specs? Here is my old Z06 with stock idle parameters (different target idle speed and RAF).

http://www.youtube.com/watch?v=Wx43GGn4Fk8

granted its a cold start, but it is all i have. 236/244 and didn't have to change anything. It never seemed to change when I changed the idle correction parameters. spark timing had the most influence. You can't tune a 427 into a 350 and you can't tune a small cam into a big cam or vice versa. The cam lope is mechanical. All you can do with the tune is make it not die and make it not idle too high. that is mostly fuel and spark.

the lopey cams are very big. my race car runs over 300 duration and 800 lift. it idles at 1000 rpm with a carb. it does not idle at 14.7 however.....

[Widebody06]

Trick Flow Track Max 291/ 295, Lift .595/ .595, Lobe Sep. 112... I'm guessing your spec is at .050" lift. Mine would be 238 int./242 exh. So nothing radical.
I'm working with the tune that came with the car and VE was changed from 400-4000, changes from stock shown below
VE_diff.jpg

As you can see my VE reduction from 1200 down was pretty large, partially because the original VE table was for catless operation and it now has MBS 200 Cpi Hiflow Cats which took it from just barely rich enough to load up to continuous loading up and CEL's. With the current reductions, its clean after 10-15 seconds of warm up(a tad lean till then) and no CEL's. No doubt its probably a bit lean on transition if you romp it but I havent and it takes throttle fine just crusing around. I will redo the VE table as soon as I can get a bung installed for my LC2.
Tunes and log:
2006 Pontiac GTO RA6 V2a1.hpt Tune as is but with a bunch of DTCs reenabled, idle lowered to 900 and loosened idle error range, not yet flashed
2006 Pontiac GTO RA6.hpt Tune I started with
OldNavy.hpl Short trip to store with original tune, idle a few mintues from the end will show loading up from richness

Sound prior to current idle tuning:
https://www.youtube.com/watch?v=G4q2GBpu7ZM

[Widebody06]

Looks like I was on the right track...have idle down to 750 with looser limits, a little less VE and its now sounds like it should, which by the way is awesome

EDIT: just realized my cam has 69* of overlap, holy crap! so next thing to really get the idle perfected is to delay EOIT till the exhaust valve is closed
Reedit: so the "real" overlap is 16 deg at .050" which puts me back to wondering why so much mixture is coming out the exhaust

[THE CHAD]

HB,

Why wouldn't you recommend "softening" the under/overspeed timing corrections at the low/mid RPM adjustment points to allow some of the natural cam lope to go unadjusted. Would reduce some of the "over correcting" and help settle the timing down on large cam setups.

Ed M

yeah mowton I agree mate, normally when you "SOFTEN" the underspeed/overspeed tables it helps greatly with idle stability especially with ''BIG CAMS/OVERLAP ETC""...That's one of the first things I do when I am tuning a ''BIG CAM/OVERLAP'' to stabilize the idle and then get on with tuning the rest etc.....

[Widebody06]

cool beans, nice to know I have my thought process going in the right direction to learn while tuning my ride. Couldnt do it without the help here....